Wireless healthcare systems, referred to as WHc systems are being used increasingly to help reduce healthcare costs, increase patient independence and provide better outcomes. FIG. 1 is a simple block diagram of a WHc system 10. The WHc system includes three main elements: wireless sensors 12a-12n, a host monitor 14, and a remote server 16. Wireless Sensors 12a-12n measure elements and the physiological signals from the body and wirelessly transmit them to a nearby device, as a host monitor 14 in FIG. 1. A host monitor 14 receives the signals and can relay them to a remote server 16 via a cellular or other type of network. The host monitor 14 could be a cell phone, portable monitor, catheter, or tissue sampling system, or the device could also be a laboratory instrument, such as a portable analyzer, point of care test kit, or any other laboratory instrument system. A host monitor 14 could be a stationary device such as a hospital bedside patient monitor, a point of care test kit or a lab instrument. The host monitor 14 could also be a portable device such as holter monitor, a glucose meter or a compact patient monitor. In emerging WHc systems 10, the host monitor 14 could be a mobile device such as a cell phone or a personal digital assistant. In all these cases the host monitor 14 can have the capability to collect data from wireless sensors 12a-12n and to perform clinical analysis on the data. The host monitor 14 could also be simply a wireless gateway or access point that collects physiological data from wireless sensors 12a-12n and simply transmit it to remote server 16 for clinical analysis. In some cases, the wireless sensors 12a-12n can have on-board processors to perform clinical analysis and occasionally communicate with the host monitor 14 and/or remote server 16.
In general, progress has been made by industry to make the host monitors 14 smaller, more capable and providing flexible networking connectivity (e.g. wireless) with remote servers 16. However, wireless sensors 12a-12n still remains a major problem. Therefore, in most cases, the patients remain tethered to host monitors, wearing traditional physiological sensors that are sending data to host monitors through wires. It is important to create effective wireless sensors 12a-12n to enable wide deployment of wireless healthcare.
Physical Monitoring
Many variables of physiological significance are measured as voltage signals (e.g. ECG, EEG, EMG, continuous glucose monitoring, electrolytes). The signals may be measured via electrodes placed variously on, within, or near a biological sample or, alternatively, integrated into a testing device. Electrodes may be placed on the skin, mounted on catheters, placed within the vascular or urinary system, inserted into biological tissue, or integrated into other devices such as invasive micromechanical devices or external analytical instrumentation used to evaluate samples of biological tissue or fluids. An electrode is a conducting connector between a biological sample and an electronic circuit, where the biological sample may be skin, tissue, blood or blood components, interstitial fluid, or urine. The material used for surface electrodes is typically silver or a silver compound which may be covered with an electrolyte for enhanced conductivity. Materials used in other sensors may vary to support sensors linked to highly specific reagents such as ion-specific resins or gels, various immunoassay formats mounted on a substrate, electrochemical or crystalline systems, or other types of diagnostic testing schemes.
Analysis of the physiological signals may be performed by any of the three devices in the system to extract the information about a person's health state—sensor 12a-12n, host monitor 14 or remote server 16. Data may alternatively be stored and later displayed for analysis by a human or computer. Analysis can also be performed in a distributed fashion, jointly by any combination of these three devices.
Wireless Sensors
Wireless sensors 12a-12n typically include one or more electrodes. What is meant by a sensor is a device containing one or more electrodes which may be placed on the skin, mounted on catheters, placed within the vascular or urinary system, inserted into biological tissue, or integrated into other devices such as invasive micromechanical devices or external analytical instrumentation used to evaluate samples of biological tissue or fluids. Furthermore, the sensor could be a patch for the surface of the skin or an implantable sensor embedded in the body.
Wireless sensors 12a-12n need to have very small form factors to accommodate patient convenience and comfort, ease-of-use and ease-of-integration into small systems. Wireless sensors 12a-12n should also be low cost, particularly if used as a disposable. These requirements call for a design that is highly integrated in every respect, including the electrode structure. To date, wireless sensors 12a-12n have been bulky, power-hungry, expensive and difficult to use.
Also, the lead placement scheme of many previous physiological measurement procedures (e.g. 12-lead ECG) is not well suited to compact integrated wireless systems. Many such systems were developed decades ago based on the electronic components available at that time and the wired connectivity. Today's electronic components are far more precise which can resolve much smaller signals from the body. The wireless connectivity also alleviates the noise picked up by long wires in wired sensor systems. Therefore, migration to wireless systems avails a fresh opportunity to create a new class of compact wireless sensors that can displace traditional bulky electrode systems used in applications such as 12-lead ECG. The present invention addresses such a need.